The present invention relates to a filtering device and in particular to a nutsch or suction filter for filtering suspensions. There is provided a horizontal filter surface arranged in a cylindrical casing. The filter surface is supported on the bottom of the casing and is constructed either as a perforated surface that is covered by a filter cloth or as a porous plate, the filter surface being subject to pressure or vacuum action.
The suction filter is a known form of intermittently operating filtering devices. Surface filtration takes place in such a suction filter and it is also possible to process suspensions with high solids concentrations. A suction filter has a horizontal filter surface, which is constructed as a screen-covered filter cloth or as a solid, porous plate. Surface filtration takes place on the filter surface, a solids layer of increasing thickness forming on the layer during filtering and which must be periodically removed. Various processes are known for removing this solid material. Apart from tilting over the suction filter and swinging the bottom down, it is known to shovel out the filter cake formed on the filter surface, for which a discharge mechanism can be used. It is known to use as the discharge mechanism a stirrer which, apart from discharging the filter cake, can also be used for flattening or smoothing out the cracks which form in the filter cake.
If it is also necessary to dry the filter cake in the suction filter, this can take place by incorporating a heating means. It is known to fit heating coils to the casing of the filtering device for supplying the necessary heat. It is also known to provide a cavity, subject to the action of a heating medium on the underside of the bottom surface on which the filter surface is supported. This heating means arranged below the casing bottom constitutes a relatively complicated solution, because a number of passages must be provided to act as a drainage system for removing the filtrate.